A conventional tire pressure sensor of a tire pressure monitoring system (TPMS) often has a data transfer device and/or a motion sensor for detecting movement of the tire pressure sensor in addition to having a pressure sensor device configured to ascertain information in respect of a pressure in an external volume of the tire pressure sensor.
A data transfer device of a conventional tire pressure sensor is often configured to transmit radio signals in an ISM band (Industrial Scientific and Medical Band), for example at a frequency of 315 MHz or 433 MHz, to an evaluating device outside of the tire. An ultra-high frequency (UHF) of that kind is generally generated using a phase-locked loop (PLL), which may also be referred to as a phase-coupled closed-loop control circuit. The phase-locked loop generates and stabilizes the emitted ultra-high frequency by using a phase comparison between a fixed, very precise reference frequency and a frequency of a voltage-controlled oscillator (VCO). The reference frequency may be provided by a quartz crystal oscillator (having a resonant frequency of 13.56 MHz) or by a MEMS resonator having a silicon structure which is caused to resonate. A MEMS resonator, which will be referred to hereinafter as a silicon resonator, is discussed, for example, in U.S. Pat. No. 6,995,622 B2.
To save energy when using a conventional tire pressure sensor, the frequency with which measurement and transmission is carried out by the tire pressure sensor is often dependent on the driving condition of the vehicle fitted with the tire pressure sensor. In that case, when rotation of a wheel fitted with the tire pressure sensor is detected by a motion sensor (i.e. when the associated vehicle is travelling), an internal pressure of the wheel will be measured and transmitted via the data transfer device to the evaluating device outside of the tire with a greater frequency than when the wheel is stationary. Examples of a motion sensor are discussed in US 2005/016722 A1 and in US 2005/0179530 A1. The motion sensor may, for example, be a ball switch and/or an acceleration sensor. The acceleration sensor may be formed using silicon and/or ceramic technology.
It should be possible for a tire pressure sensor having a suitable data transfer device and a reliable motion sensor to be produced inexpensively and in a simple manner. In addition, for installation of such a tire pressure sensor, it is advantageous for the tire pressure sensor to be of a comparatively small size notwithstanding the data transfer device and the motion sensor.